Accurate three-dimensional (3D) visualization, measurement and tracking of the location and motion (kinematics) of structures (e.g., organs, bones, markers, tools, implanted hardware, contrast agents, etc.) inside the body is important to many fields in medicine. Currently, many details of motions inside the body are unknown because systems are limited by their: ability to produce images in only two dimensions (2D), poor image resolution, slow imaging speed, and restriction on patient mobility.
Traditionally, joint motion has been measured using video-based systems that record the location of reflective markers placed on the skin while the subjects perform activities such as walking, running, rehabilitation exercises or even throwing a ball. However, the motion of the skin and underlying soft tissues does not always reflect the motion of the bones and the joints moving beneath them. For this reason, such systems may not provide the accuracy needed to measure small but clinically significant changes in joint motion. Even attaching the reflective markers to pins surgically inserted into the bones directly may result in joint kinematic errors of 2-4 mm, as others have found, far higher than the sub-millimeter accuracy necessary to measure crucial changes in joint motion. For instance, the difference between two surgical knee-ligament reconstruction techniques may be less than 1 mm of translation during walking; yet this small difference may contribute to the development of osteoarthritis after one surgical technique but not the other.
In the field of cardiac imaging, low frame rates limit the visualization of the dynamic details of the pumping heart, the fluid dynamics of the blood entering and being ejected from the heart's chambers, the flow of the blood through the coronary arteries, and/or the dynamic distention and motion of the coronary arteries during the heart beat. The ability to visualize these motions as well as measure and track the dynamic motions occurring during the heart beat may lead to improved diagnosis and treatment of heart and coronary diseases. Similarly, in the field of oncology and surgery, accurate guiding of the treatment radiation beam or surgical instrument inside the body such as the brain can mean the difference between a successful treatment and potential complications. In many other fields of medicine, the ability to visualize, track and guide, in 3D, structures and instruments internal to the body will make a significant difference in the diagnosis and treatment of disease.